Added local gemfiles for faster Travis install

.travis.yml

@@ -1,8 +1,6 @@
 language: python
 cache:
   pip: true
-  directories:
-    - /home/travis/.rvm/gems
 
 git:
   depth: 10
@@ -13,7 +11,7 @@ jobs:
         - chmod +x autopreview.sh
         - ./autopreview.sh
       install:
-        - gem install asciidoctor asciidoctor-diagram rouge
+        - gem install --local _gemfiles/asciidoctor-2.0.20.gem _gemfiles/asciidoctor-diagram-plantuml-1.2023.10.gem _gemfiles/asciidoctor-diagram-ditaamini-1.0.3.gem _gemfiles/rexml-3.2.6.gem _gemfiles/asciidoctor-diagram-2.2.14.gem _gemfiles/rouge-4.1.3.gem
         - pip3 install pyyaml aura.tar.gz
       script:
         # Fail if Asciidoctor encounters errors. Pass otherwise. Then, build updated distros